Can’t Unlink Account

I’ve been going back and forth with EA advisors for the past couple days about my EA account being hacked and unlinked from my Xbox and a new random one i can’t access being linked instead. I’ve provided information and proof about me being the Xbox account holder as well as the unlinked account holder, but it’s not good enough apparently because they want proof of ownership about the account currently linked (hacked one) which i clearly don’t have because it’s not mine. They’ve even said they can see suspicious logins and activity around the time it got unlinked. I was then told they’ve passed it onto another team for investigation but now when I try to resume the case I can’t even access the live chat because I get the usual “this issue isn’t supported by advisors.” All I want is for this random account to be unlinked, and my old one of nearly 11 years linked back to it,  surely as the console owner I should have a say in which accounts are linked to it.